Fate of Historic Landsat Mission Hinges on Upcoming Launch

View of the Landsat 8 launch site taken by Landsat 5 on Feb. 8, 2011. (USGS)

Since 1972 the Landsat mission has been monitoring natural and human-made changes to our planet. But the continuity of that scientifically precious dataset could be lost unless all goes according to plan on Monday, when the Landsat 8 satellite is scheduled to be launched into orbit from Vandenberg Air Force Base in California. Landsat 8 will take over for the hobbled 14-year old Landsat 7 that has been valiantly carrying the mission alone since December when, after 29 years in orbit, Landsat 5 began to be decommissioned after a gyroscope failure.

The launch is not likely to fail, but if it does, it won’t be the first time the continuity of the 40-year mission was jeopardized. Along the way funding has come under fire, ownership of the satellites has been transferred between government agencies and private companies, sensors have quit working, and one mission tragically failed to reach orbit. If Landsat 8 fails, Landsat 7 would run out of fuel near the end of 2016, before a replacement could be built and put into orbit.

“I’ve devoted the latter part of my career to the formulation and development of this mission,” the project’s lead scientist, James Irons, told Wired. “On Monday I go out there and look at my baby sitting on top of an enormous firecracker and hope everything goes well.”

“Yeah, I’ll be nervous.”

Technicians encapsulate the Landsat 8 satellite in its payload fairing at Vandenberg Air Force Base in California. (NASA/VAFB)

The scientists and engineers behind the Landsat mission will be hugely relieved once the craft is safely in place 700 kilometers above their heads and then begins beaming data back to Earth about a month later.

In addition to saving the mission from a gap in data, Landsat 8 — more officially known as the Landsat Data Continuity Mission — will boost the rate of coverage of the Earth and will also add more sensing capability and deliver better imagery than its predecessors.

Relying on Landsat 7 alone has meant only imaging the full Earth every 16 days. Once there are two eyes open, coverage will return to 8-day intervals, essentially doubling the resolution of landscape change that will be recorded.

“The major goal of the mission is for us to understand land cover and land use change, and determine the human impacts on the global landscape,” Irons said. “These changes are going on at rates unprecedented in human history.”

“Continuity is more important than ever.”

The new satellite will also add more sensing capability and deliver better imagery than its predecessors. Landsat 8 will measure all the spectral bands of its predecessors, but will add two new bands that are tailored for detecting the coastal zone and cirrus clouds.

The new satellite has a more advanced imaging design as well. Previous Landsat satellites used what is known as a whisk broom sensor system, where an oscillating mirror would sweep back and forth over a row of detectors that collect data across a 185-kilometer swath of the Earth. The new push system uses a very long array of more than 7,000 detectors that will view the 185 km swath simultaneously, alternately collecting light and recording data. This allows each detector to dwell on each pixel for a longer time, resulting in more detailed, accurate descriptions of the landscape.

Once Landsat 8 reaches orbit, the engineers will begin testing the spacecraft during the first week. The next few weeks will be dedicated to testing all the instruments. The satellite will then do a cross-over rendezvous with Landsat 7 to calibrate the two systems. Around day 25, the shutters will be opened and Landsat 8 will take its first look at Earth. By the end of May, the data should be flowing. The new satellite has a design life of five years, but it has enough fuel to operate for 10 years.

But first, the new craft has to get safely into orbit.

“I have a lot of assurance from everyone,” Irons said. “They are taking extraordinary care, proceeding very methodically, cautiously and rigorously.”

“Still, you realize all rocket launches have some inherent risk,” he said. “So, it’s just hold your breath and hope everything goes well.”

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